Polarization-insensitive high-contrast GaAs/AlGaAs waveguide modulator based on the Franz-Keldysh effect

A GaAs/AlGaAs p-i-n double heterostructure waveguide modulator based on the Franz-Keldysh effect is reported. On/off ratios up to 40 dB are obtained over a broad range of wavelengths (>or=32 dB between 905 nm and 960 nm), while absorption loss in the on-state is very low (<1 cm/sup -1/). The polarization dependence of the Franz-Keldysh effect is relatively weak and only causes a shift of the transmission-voltage characteristics of TE-polarized light towards higher reverse bias compared to the corresponding TM curves. Therefore, very high contrast ratios are achievable over the whole range of wavelengths even for arbitrary polarization of the light.<
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